Problems with msi r6970 lightning

Question

Hey guys I am having big issues with my 6970 lightning. Ok first I got this card to replace a second sapphire 6970 that I was running in xfire with another sapphire 6970. I since gave one of the sapphires to a relative. When I first got the lightning all went smooth benched it in a single card config then added my other sapphire 6970. No issues. Out of nowhere things rapidly went downhill. I first received a crash in grfs as I loaded shattered mountain. Froze with a sound loop then the screen turned black with a continued sound loop that eventually stopped. Reset the machine figuring it was the OC. On the lighting I had it set as 985/1400 fan 80% voltage @ 1.300 vlts. Prior to the crash I used a combo of heaven 3.0, kombustor and 3dmark 11 all passed numerous loops without issues. Again thinking it was the oc I down clocked to stock then fired up grfs multiplayer which crashed n froze on the main menu. I then  ran heaven and after 10 min a solid black screen that eventually recovered throwing a display driver has stopped responding but has recovered. Now I knew something was up.
I then ran kombustor same issues black screens sometimes a 8bit Nintendo looking screen when u need to blow in the cartridge. After countless hours of stress testing my CPU with prime, memtest, and Intel burn, I ruled out my other hardware as being the cause. I ran 2 hours of prime, Intel burn passed the maximum stress test, memtest passed until about 500% on each iteration (7 to be exact) windows version. This both with my OC and at stock. Here's for the finale I have a second machine (ill include both machines at the bottom of this post) I installed the lightening in the second rig not one single issue no black screen, no 8bit Nintendo crashes nada. Again I've tried every fix known to no prevail. Reinstalled drivers 12.10 rolled back to 12.8 used driver fusion to clear out the old remnants, swapping cards and systems. The lightning ran flawless in the old rig for hours. Now the sapphire card runs all the gpu stress tests I've tried flawlessly in the main rig at stock and OC. so I assumed the lightning was dying. But I tried the lightning in my second AMD pc (with a MSI mobo coincidentally) and it ran heaven,  kombuster, and games without a single crash.
 The only option I didn't try was taking the PSU out of the main pc and using it in the older pc to rule out the psu. But that still don't explain why the sapphire card works perfectly in the main rig and not the lightning. The second fix I didn't try was updating the mobo bios I'm using the f3 gigabyte has up to the f6 but I never had issues b4 and my sapphire 6970 and when I had two in xfire, ran perfect in the main pc with stock and oc settings, with the current PSU and bios. Food for though, gpu temps  sapphire 45c to 50c idle 75c to 80c load. Lightning 41c idle 70c to 74c load. Right where they need to be. Another thing to add I originally had a gigabyte Odin 1200 PSU that got ... Well let's say replaced (garbage of a PSU) the HX750 meets AMD requirements for xfire 6970s this almost rules out everything except BIOS or worst case the lightning just ain't compatible with the gigabyte mobo. Any ideas how to get this card to work after all the testing I know its not defective. Sry for the long post.
Main rig
AMD PII X6 1090t @4.0 with H50 push/pull 19c idle 35c load 
Gigabyte 890FX UD5 ver 2.0 bios
8GB, 2GBX1 G.Skill DDR3 1600@ 1800 9.9.9.12
1X sapphire 6970 reference and MSI R6970 lightning 900/1400- 985/1400
X-fi fatal1ty
LG bluray drive, Samsung ssdx 60gb, velci rap 150gb, WD Blk1tb, Hitachi deskstar 250 gb
Cooler master Haf X, with 4 220mm fans, vista ultimate 6
Corsair HX750 watt PSU
2nd rig
PII x4 940 blk @3.6 cooler master hyper 212 dual fan 40c idle
MSI DKA790GXM Platinum
4gb ddr2 kingston hyper x 800@960
Asus dvd burner
X-fi titanium PCI-e
2x WD raptors 150gb raid 0, WD Blk 1tb, Hitachi deskstar 250gb
Sapphire 5830 extreme @ 950/1100 1.200 vlts
Pc power n cooling 650 watt PSU
Silverstone gaming case
Windows 7 64bit

Answer 1

I also use cpuid hwmonitor to check temps n volts 12 vlt rail is at 12.05 during load. The gpu load temps on the lightning nvr exceed 72c at stock and 76c with the oc. Should I get a new mobo? Compatibility issue? I was looking at a asrock 990fx extreme 3 as this would allow me to upgrade my CPU later if I choose. I am on my current main pc bc bulldozer didn't grab me. Some benches r less than the x6s, my two 6970s perform btr than a single 7970 for my needs and the only increase I would see is if I got two 7970s that's way to much coin n would be bottlenecked by my current CPU I'm sure. Any ideas? I'm at a loss